Technical Field
This invention relates generally to ultra-low temperature freezers used in biological and pharmaceutical industries for storing biological samples. More particularly, the invention relates to improving the energy consumption of such ultra-low temperature freezers and to more efficiently use the energy that they do consume. Energy consumption is improved by providing a compact storage structure for biological sample containers and by reducing heat transfer by conduction and convection into the freezer including heat transfer during sample storage or retrieval operations. Simple defrosting and autoclaving functions are provided. The freezer heat pumping equipment is also adapted to provide HVAC functions for the room that houses multiple operating freezers thereby reducing or eliminating the cost of an HVAC system.
Background Art
Universally, large biological freezers use cascade systems to provide the cooling mechanism for obtaining low temperatures. Cascade systems are prone to failure due to oil migration, are inefficient leading to high energy costs and modulate their temperatures by switching the cooling system on and off. Reliability in this application is non-negotiable and consequently backup systems are in wide use. The inefficiency of cascade systems leads to high operating costs due to the consumption of electrical energy. For example, an 800 liter cascade freezer consumes up to 13,000 kWh per year and in many cases, even more than this. Facilities may have a number of freezers and total operating costs including the HVAC costs that are necessary to remove the heat generated from the inefficient systems, can amount to considerable expenses. Furthermore, biological freezers store samples in vials that are collected into boxes that are then placed into racks that are finally placed into an ultra-low temperature (ULT) freezer. Often times, these sample vials are hand marked and manually placed into the ULT freezer. This leads to frequent door openings, which affects temperature stability and access error due to the often-large number of sample vials that may be stored in a freezer and the manual nature of the processes of storing and retrieving them and of recording their location. Recently the company Hamilton Storage Technologies, Inc. has brought their knowledge of automation to the problem and has developed a system for auto-inventorying of sample vials in ULT freezers. Though this is a huge step forward, it is also a cumbersome system that consumes a lot of floor space thus increasing the already high energy usage per sample vial and furthermore, by placing most of the robotic movers within the cold space, reliability and life are compromised.
Therefore, an ideal biological sample vial storage and management system would have:
a. Extremely high reliability and fidelity of temperature;
b. Maximum use of facility space and minimum energy consumption in order to reduce storage costs;
c. An automatic storage and retrieval system;
d. An automatic database available on a personal computer or the Internet that tracks the sample vials and their temperature history along with associative data arbitrary or specific;
e. The system should be scalable. Meaning that units should stack as closely as possible and share the vial storage management system.